CVE-2023-29537 in Firefox
Summary
by MITRE • 06/02/2023
Multiple race conditions in the font initialization could have led to memory corruption and execution of attacker-controlled code. This vulnerability affects Firefox for Android < 112, Firefox < 112, and Focus for Android < 112.
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Analysis
by VulDB Data Team • 05/09/2026
This vulnerability represents a critical race condition scenario within the font initialization subsystem of Mozilla Firefox and its mobile variant Focus for Android. The flaw manifests during the complex process of font loading and initialization where multiple threads or processes attempt to access and modify shared memory resources simultaneously without proper synchronization mechanisms. Such race conditions create temporal windows where memory states become inconsistent, potentially leading to memory corruption that attackers could exploit to execute arbitrary code. The vulnerability specifically impacts versions prior to Firefox 112 and Focus for Android 112, indicating a widespread exposure across multiple product lines that rely on the same font handling infrastructure. The race conditions occur in the font initialization code path where concurrent access to font data structures, memory allocation routines, and resource management components creates opportunities for attackers to manipulate memory layouts and redirect execution flow. This type of vulnerability falls under the broader category of concurrency flaws that are particularly dangerous in browser environments where untrusted content is processed. The exploitation potential stems from the fact that font loading is a common operation in web rendering, making it an attractive target for attackers who could craft malicious web pages designed to trigger these race conditions during normal browsing operations. The vulnerability directly relates to CWE-362 which describes concurrent execution issues leading to race conditions, and aligns with ATT&CK technique T1059.007 for execution through web-based payloads. The memory corruption aspects of this vulnerability are particularly concerning as they can lead to privilege escalation or arbitrary code execution with the privileges of the browser process. Attackers could leverage this vulnerability by constructing web pages that force the browser to load fonts in a specific sequence that triggers the race condition, potentially leading to remote code execution on affected systems. The impact extends beyond simple memory corruption as the vulnerability could be chained with other exploits to bypass security mitigations like address space layout randomization and data execution prevention. The fix for this vulnerability required careful synchronization of font initialization routines and proper handling of shared resources to eliminate the temporal windows where race conditions could occur. This type of vulnerability demonstrates the complexity of modern browser security where seemingly benign operations like font loading can become attack vectors when concurrency issues are not properly addressed. The affected versions represent a significant security gap that required immediate patching across multiple platforms, highlighting the importance of thorough testing of concurrent code paths in security-critical applications. The vulnerability underscores the need for comprehensive security testing that includes race condition detection in high-risk areas such as memory management and resource initialization processes.